The present invention is related to compositions which may be used in methods for detection and/or surgical therapy associated with solid, non-lymphoid tumor types. More particularly, the present invention is related to peptides having binding specificity for shed mucin, and their use for detecting lymphoid tissues, which contain deposits of shed mucin, and which are involved in promotion of tumor cell invasion and metastasis.
1. Immunopathology
The response of an individual to tumor cells involves the reactions and counteractions mediated by both cellular and humoral arms of the immune system. Tumor cell growth may represent a disturbance in the equilibrium of the immune system that is pre-existing, and/or induced by the tumor cells themselves. However, most investigations to date have focused on the role of T cells in tumor immunity. The role of B cells in a tumor-bearing individual still remains unclear.
Previous studies have shown that lymph nodes regional to a primary tumor in cancer patients, and in in vivo experimental animal models of tumor development, can undergo a prominent expansion in the germinal centers of immune cells that include B lymphocytes (B cells) (Eremin et al., 1980, Br. J. Cancer 41:62; Bertschmann et al., 1984, Br. J. Cancer 49:477-484). However, the reason(s) for this observed B cell proliferative response remains unclear, and may be due to either activation and stimulation directly by tumor cells or tumor cell components, and/or indirectly by stimulation of T-helper cells which then activate and stimulate B cells. A recent study confirmed the increase in the number of B cells in lymph nodes regional to primary tumors (Ito et al., 1996, Immunobiol. 195:1-15). The number of B cells increase in the regional lymph nodes concomitantly with tumor development, and such B cells appear to be able to elicit anti-tumor immunity. In that regard, there are numerous reports that cancer patients have circulating antitumor antibodies (see, e.g., Carey et al., 1976, Proc. Natl. Acad. Sci. USA 73:3278-3282; Abe et al., 1989, Cancer Res. 80:271-276; Christensen et al., 1989, Int. J. Cancer 37:683-688). Thus, there appears that a humoral immune response towards tumor-associated antigens can be mounted in cancer patients. However, the role of the B cells in the host response to tumor, and the tumor associated antigens recognized by B cells, remain poorly defined.
2. Current Diagnostic and Therapeutic Implications
Several techniques, such as radioimmunodiagnosis and radioimmunoguided surgery, have been developed for the purpose of detecting tumors occult to other imaging techniques. In radioimmunodiagnosis, a patient is injected intravenously with a radiolabeled antitumor monoclonal antibody or radiolabeled antibody fragment with binding specificity for the tumor. Hours to days post-injection, the patient is then examined by immunoscintigraphy for body imaging of primary tumor and metastases. Radioimmuno-diagnosis continues to be evaluated for preoperative evaluation of patients (Ryan, 1993, Cancer 71:4217-24). In radioimmunoguided surgery, a patient is injected with a radiolabeled anti-tumor monoclonal antibody, and exploratory surgery is carried out approximately 3-4 weeks post-injection. The 3 to 4 week period allows for the patient to clear radioactivity that is unbound to tumor cells (xe2x80x9cbackground signalxe2x80x9d). The surgeon uses a hand-held radiation detector to detect localized high counts of radioactivity representing tumor foci. These radioactive areas subsequently found visually or histologically to contain tumor cells are then resected or excised. U.S. Pat. No. 4,782,840 describes the radioimmunoguided surgery protocol in more detail. Another radioimmunoguided surgery protocol using antibody fragments for close range tumor detection, in detecting and defining tumor and tumor margins, is described in more detail in U.S. Pat. No. 5,716,595.
Using either radioimmunodiagnosis (RAIDS) or radioimmunoguided surgery (RIGS) to search for metastases from colorectal or ovarian cancer, false positivity of draining lymph nodes has been observed (for a review, see Cornelius and West, 1996, J. Surg. Oncol. 63:23-35; Stephens et al., 1993, J. Nucl. Med. 34:804-08; and Sivolapenko et al., 1995, Lancet 346:1662-1666). At the time of the invention, it was believed that such false positive tests result in surgical dissections that will not benefit the patient, but instead, will increase morbidity. Therefore, false positive tests xe2x80x9cshould be diligently avoided in the surgical patientxe2x80x9d (Stephens et al., 1993, supra). For example, since false positive lymph nodes are not easily examined by palpation, such false positives are currently viewed as presenting a serious problem to general applicability of radioimmunodiagnosis and radioimmunoguided surgery (Stephens et al., 1993, supra).
False positive (xe2x80x9cfalse tumor-positivexe2x80x9d) lymph nodes (LN) have been characterized as germinal center staining for noncellular tumor antigen; and classified as type III: RIGS positive, histology (hematoxylin and eosin) negative for tumor. It is estimated that of the lymph nodes detected by RAIDS or RIGS, 80% are false positive (i.e., lack evident tumor cells but contain noncellular tumor antigen). Several mechanisms to explain such false positives have been proposed. One suggested mechanism is that shed tumor antigen causes an inflammatory process mediated by the tumor antigen/antibody complex that may also involve a T cell-mediated cytotoxic response (Stephens et al., 1993, supra). Alternately, tumor antigen is retained in the form of antigen/antibody complexes, attached to follicular dendritic cells located in the germinal centers (Cornelius and West, 1996, supra). In another proposed scenario, tumor antigen detected is primarily in sinusoidal macrophage as part of antigen processing (Cornelius and West, 1996, supra). The phenomenon of false positives is problematic, and needs to be further investigated to identify its origin and to explain its relationship, if any, to treatment options, and resultant clinical outcomes following treatment, for the affected patient.
3. Need for New Therapeutic Approaches
While new therapeutics are being developed and tested for efficacy, many of the currently available cancer treatments are relatively ineffective. It has been reported that chemotherapy results in a durable response in only 4% of treated patients, and substantially prolongs the life of only an additional 3% of patients with advanced cancer (Smith et al., 1993, J. Natl. Cancer Inst. 85:1460-1474). Current treatments for metastases are both cost-prohibitive, relatively ineffective, and present with major toxicity. Regarding the latter and depending on the drug or drug combination used, systemic chemotherapy may result in one or more toxicities including hematologic, vascular, neural, gastrointestinal, renal, pulmonary, otologic, and lethal.
Surgery, when possible, is used as a standard therapy for patients with isolated metastases (e.g., hepatic and/or pulmonary). After resection, the projected five year survival rate may range from 25-35%, the mean survival is about 31 months, and the 30-day mortality rate is about 4% (Wade, 1996, J. Am. Coll. Surg. 182:353-361). However, about 25% to 45% of patients who have had resection of their colorectal cancer later develop recurrences (Zaveidsky et al., 1994, supra). Thus, there continues to be a need for identifying processes which enhance tumor growth and metastasis. More particularly, there remains a need for a method of detecting and treating processes that contribute to tumor development at an early stage (e.g., Stage I or II) or late stage (e.g., Stage III or IV) before, during, or after surgical resection of tumor. Likewise, there remains a need for a method of detecting and treating precancerous conditions (e.g., prior to, or at an early stage of, development of primary tumor or regrowth).
Accordingly, it is a primary object of the present invention to provide compositions that may be used to detect mucin or other shed tumor antigens containing Tn antigen in a method for detecting a pro-tumor immune response in an individual.
It is a further object of the present invention to provide compositions that may be used to detect localized shed tumor antigen in lymphoid tissues involved in a pro-tumor immune response, wherein lymphoid tissues detected as containing shed tumor antigen are then surgically removed from the individual being treated.
It is also a further object of the present invention to provide compositions which can be used to detect lymphoid tissues involved in a pro-tumor immune response, wherein such detection is a prognostic indicator that invasion and metastasis has occurred, or is likely to occur, from the local primary tumor.
The foregoing objects are achieved by identifying a novel mechanism in which mucin and mucin-like molecules, shed from tumor cells of solid, nonlymphoid tumors, are capable of inducing an immune response which promotes tumor growth and metastasis, as will be more apparent from the following description. This mechanism of tumor promotion involves the specific type of immune response induced by shed tumor antigen (mucin and mucin-like molecules containing Tn antigen). This specific immune response, a xe2x80x9cpro-tumor immune responsexe2x80x9d, can involve (a) the contact or presence of shed tumor antigen in relation to the cell surface of B cells, and cell surface of follicular dendritic cells or other antigen presenting cells (e.g., contained in lymphoid tissues); (b) activation of such B cells to proliferate, (c) and differentiation of the activated B cells into plasma cells which secrete anti-shed tumor antigen antibody that forms complexes with shed tumor antigen in sufficient amounts which may act indirectly (via immune effector cells) and/or directly (on the tumor cells) to mediate tumor progression. Continuous presentation of immune complexes containing shed tumor antigen by FDC plays an important role in the persistence of a pro-tumor immune response.
In one embodiment of the present invention, a composition having binding specificity for shed tumor antigen is used to find and bind to shed tumor antigen localized in lymphoid tissues in an individual. The lymphoid tissue containing shed tumor antigen may then be surgically excised from the individual, thereby immuno-modulating the immune system to prevent the tumor promoting function of the pro-tumor immune response.